This disclosure relates to a recording medium discharge device and an image forming apparatus, and in particular, relates to control of an ascending and descending operation for a stacking unit during discharge of a recording medium.
Conventionally, an image forming apparatus includes a recording medium discharge device that discharges a recording medium after completion of image formation or after post-processing such as a punching process and the like, and in which a recording medium discharge tray receives and stacks the discharged recording medium. In this recording medium discharge device, when a disturbance occurs in the stacking state of the recording medium during recording medium stacking into the recording medium discharge tray, the recording medium is not stacked properly into the recording medium discharge tray. As a result, when it is detected that the upper surface of a recording medium bundle that is stacked in the recording medium discharge tray is not in the correct vertical orientation relative to the recording medium discharge port by using a detecting sensor, a technique is adopted by which the upper surface of the recording medium bundle on the recording medium discharge tray is corrected to a correct vertical orientation by raising after the recording medium discharge tray is lowered by a fixed amount.
Conventionally, a technique is disclosed in which, for example, even when the recording medium discharge tray is lowered by a fixed amount, if the upper surface of the recording medium that is on the recording medium discharge tray continues to be detected in the same predetermined position as prior to the lowering operation, the recording medium discharge tray is further lowered by the predetermined amount. The lowering operation by a predetermined amount is executes for at least a regulated number of occasions, and when the upper surface of the recording medium is no longer detected at the predetermined position, the recording medium discharge tray is raised again until the upper surface is detected, and the fall height of the recording medium into the recording medium discharge tray is maintained at a fixed level (Prior Art 1).
A further conventional technique is disclosed in which the recording medium is discharged and the recording medium discharge tray is lowered to the predetermined position. Even after the lowering operation, in the event that the upper surface of the recording medium bundle in the recording medium discharge tray continues to be detected at the predetermined position, the recording medium discharge tray is again lowered, and at the point in time when the upper surface of the recording medium is no longer detected at the predetermined position, the recording medium discharge tray is switched to a raising operation (Prior Art 2).
A further conventional technique is disclosed in which the recording medium on the recording medium discharge tray can be correctly detected, even when a gap is produced between the recording media stacked on the recording medium discharge tray, by forming a projection that is high in comparison to the other positions on the recording medium stacking surface. The projection is formed in a position that shields the light axis connecting the light emitting portion and the light receiving portion of a light sensor that detects the presence or absence of the recording medium in a region including the recording medium stacking surface of the discharge tray (Prior Art 3).
The configuration in Prior Art 1 and 2 above enables falling of the recording medium rear end into the recording medium discharge tray and correctly stacking the recording medium in the recording medium discharge tray by repeated performance of a lowering operation of the recording medium discharge tray as described above upon occurrence of a state in which the rear end of the recording medium that is discharged from the recording medium discharge port into the recording medium discharge tray cannot fall from the recording medium discharge port into the recording medium discharge tray. However, a solution is not provided in relation to a fault such as a paper jam in the periphery of the recording medium discharge port resulting, for example, from a level difference caused when, in the recording media that have fallen and been stacked into the recording medium discharge tray, the upper portion of the recording medium is stacked in an orientation that deviates from the other recording media and the upper surface of the recording media stacked in the stacking portion is not flat.
The configuration in Prior Art 3 above cannot accurately detect the recording medium position when a gap between the recording media is produced at a position separated from the light axis between the light emitting portion and the light receiving portion provided with a sensor for detecting the presence or absence of the recording medium, and therefore the technique disclosed in Prior Art 3 also cannot provide a solution to a malfunction such as a paper jam occurring in the periphery of the recording medium discharge port due to a difference in level in the height of the upper surface of the stacked recording media as described above.